THE ASPERGILLUS CANDIDUS GROUP 207 



collected from nature from world-wide sources, strains characterized by 

 heads approaching white are occasionally observed in other groups. It is 

 apparent, then, that the capacity to produce a coloring substance, while 

 ordinarily inherited or passed on in successive colonies of an organism, is 

 not always uniformly maintained. 



In the present treatment, the writers have sought to include within the 

 Aspergillus Candidas group only such forms as are clearly and closely related 

 to it. The group is thus limited, essentially, to a single series containing 

 only one clearly definable species, A. candidus. Different isolations vary 

 materially in their general cultural appearance and in the details of their 

 microscopic structure. Nevertheless, all possess the typically globose, 

 white to dull buff or light gray conidial heads, the smooth colorless coni- 

 diophores, and the small, smooth, colorless conidia. 



To facilitate recognition of members of the Aspergillus candidus group 

 and to assist in the proper assignment of other white or light-colored 

 species and strains, a general key covering all of these forms is presented. 



GENERAL KEY OF WHITE ASPERGILLI 



A. Heads (large ones) globose or radiate; conidiophores smooth-walled, colorless or 



yellowed toward the vesicle only; sclerotia occasionally seen A. candidus group 



B. Heads white, hemispherical to columnar; conidiophores smooth-walled, colorless 



A. niveus series, see p. 202 



C. Heads initially white, tending to be columnar; conidiophores smooth-walled, 



showing some shade of yellow; contorted hulle cells usually found 



A. flavipes, series, see p. 179 



D. Heads white, borne upon long, smooth-walled, colorless conidiophores terminat- 



ing in clavate vesicles, sterigmata in two series 



White-spored phase of A. janus, see p. 187 



E. Strains of white Aspergilli possessing the basic characters of their colored counter- 



parts also occur as mutations in the A. fumigatus, A. nidulans, A. terreus, and 

 glaucus groups. 



Aspergillus candidus Link, Obs. p. 16, 1809. Thorn and Church, The 



Aspergilli, p. 157. 1926. 



Colonies upon Czapek's solution agar persistently white, or becoming 

 cream or yellowish-cream in age (PI. VI A and fig. 59), often thin, veg- 

 etative mycelium often largely submerged, surface growth usually con- 

 sisting of conidiophores and heads, and with scanty sterile mycelium or 

 anastomosing ropes of hyphae bearing short-stalked fruiting structures; 

 sclerotia produced in occasional strains; reverse usually uncolored. Heads 

 white, globose, radiate, varying in the same culture from large globose 

 masses 200 to 300m in diameter to small heads often less than 100/x in 

 diameter, commonly more or less elongated in heads with incomplete de- 

 velopment of sterigmatic surface. Conidiophores varying with the strain, 



